The plant hormone ethylene plays an important role in plant development and is a major component of a plants response to physical and biological stress. This simple hydrocarbon molecule provides an effective stress signal; its gaseous nature allows for rapid diffusion of the hormone signal to both local and distant target sites where upon activation of stress and defense response genes may aid in plant protection. The ethylene-related mutants of Arabidopsis thaliana are powerful tools for the genetic dissection of the ethylene signal transduction pathway. Mutations which affect hormone production, perception and signal transduction will be examined. The role of etheylene in plant stress and differential cell growth processes will be addressed using genetic, molecular and biochemical approaches. Our understanding of the mechanisms of hormone signal transduction will be greatly aided by analysis of the Arabidopsis ethylene-related genes. The molecular cloning and characterization of genes which are required for regulation of ethylene production, perception and signal transduction is a major focus of this proposal. The effects of ethylene-related mutations on hormone- and stress-regulated gene expression will be examined using chimeric gene fusions and in situ RNA hybridization. The ability to resist bacterial pathogen attack will also be investigated in these mutants. Finally, to further aid in the genetic dissection of the ethylene action pathway, pseudorevertant analysis will be initiated for genes which act at different steps in the signal transduction process. The characterization of interactions among ethylene receptors, effector molecules and modulatory components at the genetic, molecular and biochemical level should provide insight into the complex pathways of hormone signal transduction.
